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The operation of a CPU is determine by the instruction it executes, referred to as machine instructions or computer instructions. The collection of different instructions is referred as the instruction set of the CPU.

Each instruction must contain the information required by the CPU for execution. The elements of an instruction are as follows:

Operation Code:
Specifies the operation to be performed (e.g., add, move etc.). The operation is specified by a binary code, know as the operation code or opcode.

Source operand reference:
The operation may involve one or more source operands; that is, operands that are inputs for the operation.

Result operand reference:
The operation may produce a result.

Next instruction reference:
This tells the CPU where to fetch the next instruction after the execution of this instruction is complete.

 
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